You may be surprised to hear that Microsoft began the bulk of the Xbox One in late 2010. It took the company less than three years to reveal the new console to the public.
Sr. Principal Creative Director at Xbox Carl Ledbetter said:
“We started back in 2010; late 2010. And got the team together and really had fun. At the beginning, we created a number of concepts and we started really refining those ideas.”
We do know that Sony began “thinking about” the PlayStation 4 in 2007. When development actually began isn’t entirely clear, however.